1. Field of the Invention
This invention relates to electro-active transducers. More specifically, the invention is an electro-active transducer that generates out-of-plane motion when a radial electric field is induced in the plane of the transducer, or that converts applied out-of-plane motion into a radial electric field in the plane of the transducer.
2. Description of the Related Art
Solid-state transducers generally make use of electro-active materials. In the case of an actuator, the electro-active material generates physical displacement in response to an applied voltage. In one embodiment, these actuators are planar and have one or more pieces of ferroelectric material (e.g., piezoelectric, piezostrictive, pyroelectric, etc.) with one or more electrodes coupled thereto. The plane of the actuator is typically referenced as the “X-Y” plane with the “Z” direction being perpendicular thereto. In terms of an actuator, with the electrodes lying in the X-Y plane, the electric field (induced when voltage is applied to the electrodes) will also lie in the X-Y plane. Displacement of such actuators will also occur in the X-Y plane. Thus, in terms of the device's piezoelectric charge constant, these devices are said to be “d11”, “d21”, “d12”, or “d22” where the first subscript refers to the direction of applied field strength and the second subscript refers to the direction of measured induced strain. The numbers 1, 2, and 3 correspond to the X, Y, and Z directions, respectively. To summarize, the induced electric field and corresponding displacement are essentially co-planar for such solid-state planar-types of actuators. The opposite would be true in terms of planar-types of sensors. That is, in-plane displacement would generate an in-plane electric field indicative of the force creating the in-plane displacement.
Transducers may also function in a situation where out-of-plane displacement (i.e., in the Z direction) is caused by the application of an electric field in the X-Y plane. In such situations, the transducer behaves as a “d13” or “d23” device.